Field of the Invention
The present invention relates to seals for the joining of pipes. More specifically, the invention relates to a lip seal for sealing a space connecting a socket of one pipe to the spigot of another pipe.
Description of the Related Art
Pipe seals have been designed for the sealing of structured wall pipes (SWP). Exemplary structured wall pipes include double wall corrugated pipe. The pipe seal is located in a first groove or channel of the spigot pipe. After assembling the pipes, the seal seals the space between the socket of one pipe and the spigot of the other pipe. However, there is no standard size for the groove. For example, the size and shape of the groove may range from small to large and/or from wide to narrow. Thus, there is a wide range of groove shapes and sizes for structured wall pipes.
Pipe seals for structured wall pipes can have a cross-sectional shape that is symmetrical or non-symmetrical. Symmetrical seals avoid the problem of the operator placing the seal backwards in the groove of the spigot pipe prior to assembly of the pipes. Non-symmetrical seals rely on the operator to correctly orient the seal in the groove of the spigot pipe. The sealing ability of a non-symmetrical seal incorrectly placed in the groove may be compromised.
Pipe seals can be classified as lip seals or compression seals. Rubber of the lip seal is bent during assembly of the pipes. In contrast, rubber of the compression seal is pushed or compressed down during assembly of the pipes. In certain applications, lip seals provide advantages over compression seals. For example, lip seals have less rubber volume, are easier to stretch onto the spigot of the pipe, ease assembly of the pipes especially pipes with smaller gaps, require lower assembly force, and are self-locking (no push back).
However, SWP with wide grooves are difficult to seal using symmetrical lip seals. Symmetrical lip seals have a tendency to rotate in the wide groove during assembly jeopardizing the pipe seal's sealing function.
Accordingly, there is a need for a symmetrical pipe seal that is resistant to rotating during assembly even within wide grooves.